The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hybrid electric vehicles can selectively use different energy sources as needed in order to achieve optimal fuel efficiency. A vehicle can selectively use either or both an internal combustion engine and a motor/generator unit(s) connected to a high-voltage battery module or energy storage system for propulsion and operational control.
One vehicle includes a hybrid powertrain including an engine stop/start system wherein the engine automatically shuts down during ongoing vehicle operation and automatically restarts using an electric motor/generator unit. The system preferably includes a regenerative braking system for recharging the high-voltage energy storage system via the electric motor/generator unit and the ability to selectively shut down the engine during vehicle idle, referred to as an Auto Stop control scheme.
The motor/generator unit can be used as a belt-alternator-starter (BAS) system in place of an alternator. The BAS applies torque to a serpentine belt of the engine when an operator signals an intention to resume travel after executing an Auto Stop control scheme. Torque from the motor/generator unit(s) can spin the engine for a short duration to crank the engine until it fires and runs. During cold starting of the engine, a crankshaft-mounted auxiliary or 12-volt starter motor can provide cranking torque to crank and start the engine. Known BAS systems use a high-voltage energy storage system supplying high-voltage electrical power through a voltage inverter to the motor/generator unit(s). The high-voltage battery can be temporarily disconnected or otherwise rendered unavailable due to a fault or other operating conditions. This may result in a loss of or an insufficient field excitation, especially for an asynchronous machine-based electric motor/generator unit, which in turn can result in a loss of sustained auxiliary electrical power generation aboard the vehicle. Insufficient auxiliary electrical power can result in a vehicle shutdown leading to a walk-home event.